[sdiy] AS3280 test

Ian Fritz ijfritz at comcast.net
Sun Nov 11 06:54:09 CET 2018


Tim --

Good question. I guess it comes down to statistics. Specs on the older devices were all over the map, so some careful testing and selecting were needed to get really good performance. That being said, I once got a batch from Futurlec that all had very low feedthrough. I'm hoping the new Alpha units will have tighter parameter spreads.

Ian

> On Nov 10, 2018, at 9:33 PM, Tim Parkhurst <tim.parkhurst at gmail.com> wrote:
> 
> We are truly spoiled for choice these days. Who would have figured we would see the relatively inexpensive reissue of the 3080, various and sundry CEM and SSM chips, AND now the 3280? Along with the 13700 and 2164 chips that have never really gone away, the analog designer's toolbox is full of wonderful options these days. 
> 
> Question: Does the improved linearity of the 3280 mean that it will perform better in VCO applications than the 3080 and 13700? 
> 
> Thanks for the update, Ian. :)
> 
> 
> Tim (I'm not spoiled, I just smell that way) Servo
> 
> 
> 
> 
> 
>> On Sat, Nov 10, 2018 at 2:21 PM Ian Fritz <ijfritz at comcast.net> wrote:
>> Hello --
>> 
>> Good news! Alex sent me a couple of his AS3280 chips, and they work great!
>> 
>> I didn't do extensive testing, just a couple of measurements in my usual 
>> test configuration, which is a standard VCA circuit. I benchmarked them 
>> against a CA3280 that had previously been selected for high performance, 
>> and against typical results for older devices.
>> 
>> Configuration: The input diode pins are fed a 1 mA current. The input to 
>> the control pin is 0 - 0.5 mA, and the output current is the same. The 
>> I-V converter output is 0 - 2V.
>> 
>> With the offset nulled at full gain, the variation in output voltage 
>> with Iabc is under 1 mV. My standard for a very good device is under 2 mV.
>> 
>> Output linearity vs Iabc was better than 1%, with two devices near 0.1% 
>> Devices I tested previously were mostly around 2%. So it shouldn't be 
>> too hard to select devices for critical multiplier applications.
>> 
>> Thank you Alex!
>> 
>> Ian
>> 
>> 
>> 
>> 
>> -- 
>> ijfritz.byethost4.com
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